Pattern forming technologies used in semiconductor and display industries are classified into 3 categories. One is a subtractive method mainly applied to thin film technologies such as CVD, PVD and sputtering wherein a metal layer is deposited on a substrate, a photo-resist layer is patterned by lithography on the metal layer, and then the metal layer is etched as a pattern. Another is an additive method used in thick film technologies such as screen-printing. The other is a subtractive-additive method adopting both of a subtractive method and an additive method. Pattern forming by an additive method is an economic process, which spares material and decreases number of steps, but additive methods of thick film technologies such as screen-printing are not so fine as thin film technologies, and thus are applied to different processes.
If an additive method accomplishes finer patterns, it is more favorable in aspects of environment and cost reduction. For example, attempts to apply an additive method to pattern forming for color filters originally formed by thin film technologies have been made. In this context, pattern forming by inkjet printing has been recently noted.
MOD material has been researched since Vest, R.W. tested inks made of MOD material (IEEE Transactions on Components, Hybrids and Manufacturing Technology, 12(4), 545-549, 1987). Kydd, et al in WO98-37133 disclosed inkjet-printing ink consisting of MOD material and particulate metal. U.S. Pat. No. 6,878,184 owned by Kovio Inc. disclosed metal ink of nano-size particle prepared from MOD and a reductant (for example, aldehydes). Many attempts have been made to use ink containing dispersed fine metal particles, especially silver particles for forming electrically conductive pattern. A new inkjet-printing system including nozzles should be devised with inks dispersed with fine metal particles, i.e., fine silver particles because those behave differently from ordinary inks. In addition, additives added to sustain suspension would do harm to the physical properties of patterns formed.
In the above-mentioned respect, inks containing MOD (metallo-organic de-composition material) can be applied to traditional inkjet printing devices without severe modification of the system if those are thoroughly solution. Solution inks containing MOD, in addition, can lower the temperature of metalization, and thus can be applied on flexible substrates such as plastic.
Korean Patent Publication No. 2004-85470 applied by Haeuncomtec disclosed a metal ink for inkjet-printing consisting of 5˜40 t % of silver oxide, 10-20 wt % of lactam, lactone or carbonate and 20-85 wt % of amine. The ink prepared in the example is likely suspension rather than solution considering the dark color of the ink. Emulsifier which may do harm to the physical properties of patterns formed, should be added to the ink to sustain suspension, In addition, maintenance problems concerning nozzle clog caused by particles may arise.
Prior arts published to date are listed below as Table 1 and Table 2.
TABLE 1Patent DocumentsApplicationDate(Publicationor RegistrationNo.CountryApplicant(Inventor)Title of InventionNo.)Technical Features1)USEngelhard(Pascalinemetallized1986, 9, 10(Pat. No.Metal carboxylate,Nguyen)substrates and4808274)alcoholate,process formercaptide,producingamino + carboxylate,acyl + carboxylate,alkoxide2)US(Michael G.Seed layer compositions1990, 4, 27(Pat. No.metal bonded toFirmstone,containing5059242)hydrocarbonet al)organogold andthrough thio,organosilverpolythio,compoundscarboxylate bridge3)USDegussaGold(I) mercapto-1993, 4, 5(Pat. No. 5312480)gold(I)mercaptocarboxyic(Lotze;carboxylic acidacid esterMarion)esters, method ofused for ceramictheir preparationgold decorationand use4)PCTParelec,Material andInternational ApplicationmetalInc. (Kydd;method for1997, 9,powder + MOD orPaul H. □□)printing high conductivity12(internationalROM (reactiveelectricalpublicationorganic medium);conductors andWO98-37133)MOD is defined asother componentsorganic materialon thin filmbonded to metaltransistor arraysthrough heteroatoms such as O,N, S, P, As and Se5)USKovio, IncNanoparticle2002, 8, 9(Pat. No.particulate ink(Rockenberger;synthesis and the6878184)prepared byJoerg)formation of inksreducing MOD(ortherefrommetal powder +RMO) withaldehydes6)SouthhaeuncomtecOrganic silver2003, 03, 28(Publication5-40 wt % ofKorea(Kwangchun-composition,No.Ag + 10-20 wt % ofJung)preparing method2004-84570)(lactam, lacton ortherefor, inkscarbonate + 20-85 wtprepared% of aminetherefrom andmethod forformingconductive circuitwith use thereof
TABLE 2Nonpatent DocumentsNo.authorTitle of ArticlePublication dateTechnical features1)Teng, K. F.,Liquid Ink JetIEEE TransactionsMOD is mentioned as organicandPrinting with MODonmaterial bonded to metalVest, R. W.Inks for Hybrid MicrocircuitsComponents, Hybridsthrough hetero atoms such asand MamufacturingO, N, S and P Specifically,Technology,silver neodecanoate and Au12(4), 545-549,amine 2-ethylhexoate is examplified.1987Dielectric ink andresistance ink are mentioned2)LeaDirect Write Metallizations2000, 8, 18 undergraduate(hfa)Ag(COD),Yanceywiththesis of(hfa)Cu(BTMS)OrganometallicBerkelyand(hfa)Cu(VTMS) areInksUniversityspayed or printed by inkjetprinting on heated glassannealed and resistance aretested3)C. Curtis,Metallizations byTo be presented at(hfa)Ag(COD)Direct-Writethe NCPVInkjet PrintingProgram ReviewMeeting Lakewood,Colorado14-17October 20014)AlexSynthesis of SinglePeer-ReviewedSrCu2O2 from MOD(copperMartinsPhase SrCu2O2scienceformate and strontium acetate)onfrom LiquidJournal 2004, 3, 3is printed and annealed atPrecursors770° C. used as photosemi-conductor of solar cell5)KevinInk-Jet Printing,Macromol. Rapidlaminating polymerCheng,*Self-AssembledCommun. 2005,electrolytes PAA and PAH byPolyelectrolytes, and26, 247-264PEM technology andElectroless Plating:patterning the laminar withcatalyst Na2PdCl4 anddeposit in copper bathelectolessly. lower metalizationis possible